n,m,k=map(int,input().split())
l=[list(map(int,input().split())) for i in range(m)]
d=list(map(int,input().split()))
c=[[] for i in range(n)]
for i in range(m):
  c[l[i][0]-1].append((l[i][1]-1,l[i][2]))
  c[l[i][1]-1].append((l[i][0]-1,l[i][2]))

dp=[[0]*n for i in range(k+1)]
for i in range(n):
  dp[0][i]=1
for i in range(1,k+1):
  for j1 in range(n):
    if dp[i-1][j1]==1:
      for j2 in range(len(c[j1])):
        if c[j1][j2][1]==d[i-1]:
          dp[i][c[j1][j2][0]]=1
ans=[]
for i in range(n):
  if dp[-1][i]==1:
    ans.append(str(i+1))
print(len(ans))
print(' '.join(ans))